1 Abstract -The grid frequency regulation function addresses the balance between the network's load and power generated. The intent is to maintain the grid at the target 50Hz or 60Hz operating point. When there is more load than generated power, frequency drops, and vice versa. The system operator generates a signal, Area Control Error (ACE), based on the difference between load and power. Traditionally, frequency regulation is managed by varying the output of fossil fuel or hydro generators connected to the electric grid. A new method in which electrical energy is stored in high speed flywheels and then is recycled to keep the system in balance, first, absorbing energy when it is in abundance, then discharging when there is a power shortfall. The cost and performance of storage-based regulation can offer significant advantages over traditional generator-based regulation. Availability of this new grid technology is particularly important, since the rapid addition of variable-generation renewable resources to meet RPS standards is expected to increase the need for regulation.The advantages primarily come from very fast response from the flywheels, measured in 100% power response in under 4 seconds as compared to up to a 5 minute response characteristic of a conventional regulating generator. An interconnection study was performed by National Grid to evaluate the impact of such rapid fluctuations on a 23kV distribution line.

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